Let me commence with an explanation and an apology. About a year ago we were discussing the Annual Report of the Advisory Committee for Aeronautics for 1918é19, and I suggested that in that report was ample material for an interesting Paper dealing in great measure with advances during the war; material which up to then had been strictly confidential in character. Some few months ago an invitation came to me from your Council to read such a Paper, and I hastily accepted.

Six weeks ago I sat down to put my ideas in form and wrote some few pages when it suddenly occurred to me that Prof. Bairstow, in his Wilbur Wright lecture last year, had dealt with the subject in a most able and complete way and with very full knowledge, and that I had but little to add to his admirable exposition.

The following extremely important table, compiled by Major Linton Hope, was inadvertently omitted from the reprint of his lecture in the August issue of the Journal. It should also be noted that the last set of Flying Boat lines, on page 470, is the design which Major Linton Hope made in 1916, after the trials of the 41ft. design, Fig. 2, and to which he refers in his reply to Mr. Baker. It should be noted that the angles of the step tangents to the foreplaning bottom have been increased and the back step reduced in size and moved aft, both of which features appear in C.E.I. designed some considerable time afterwards.

The resistance offered by bodies to motion through fluids has for many years been a problem of the first importance, and one which has received a correspondingly large degree of attention both from scientific investigators and those commercially interested in the subject. A considerable amount of mathematical investigation has been carried out; but a detailed study of fluid motion has only proved possible in the case of a perfect fluid, i.e., one in which viscosity is not present. Assumptions have been made as to the quantities upon which the motion of the fluid and the body depends, and formulæ have been prepared expressing the laws connecting force and speed for dynamically similar bodies.

In the present note attention will be directed chiefly to the case where the only properties of the fluid upon which the motion depends are the viscosity and density, though brief mention may be made of instances where the acceleration due to gravity is also important.

The inclusion of incidence wires in strength calculations, by the method of strain energy, makes very little difference in normal flight conditions, but shows, large changes in wing loads in nose diving and in centre section loads with a broken flying wire. There is a serious increase of load in the bottom plane in nose diving.

During the war a heavy demand was made on the supplies of aeronautical timber, and in order to allow of the use of smaller sized timber, it became necessary to permit the introduction of splices into aeronautical construction. We knew of no means to obtain accurate comparative data, and the purpose of the present inquiry (with which Captain K. Robertson was also associated) was that of finding a method of splicing timber beams which should prove to be the most effective for withstanding bending moment (as in aeroplane main plane spars) and which should at the same time be simple to produce and easy to inspect.

As a preliminary step we invited suggestions from aircraft constructors and others as to the forms of splices which, in their opinion, were likely to give the most useful results.